This proposal focuses on the normal and abnormal development of two mid-level feature integration mechanisms in human visual cortex. These mechanisms will be studied using a combination of psychophysical and non-invasive electrophysiological methods. The first Aim examines the integration of local orientation information along closed contours. Thresholds for contours embedded in noise will be measured in normally developing infants, visually mature patients with a history of amblyopia and in normal adults. The second Aim examines the integration of local motion signals into coherent global motions. Normally developing infants and patients with amblyopia will be studied. The extraction of local features appears to develop relatively early, but integration of features may emerge substantially later and at different times for different types of object-related information. Objective methods of characterizing feature integration mechanisms may provide a better description of the deficit in amblyopia than currently available measures of contrast sensitivity or resolution. These new measures may prove useful in the monitoring of the effectiveness of amblyopia treatment in pre-verbal populations.